Doug;
As a fabricator, here's the scoop;   its Yes and No as to whether there's a cost difference.

If your designs require the tolerances of LPI mask, then it will cost more to change colors. The reason is that the LPI process is a BATCH process.   Every pcb, regardless of design, is flooded with mask using the same setup. It is later exposed with your custom film in an exposure unit.   A color change requires an extra silkscreen tear-down and setup...Actual costs vary from shop to shop.   In our case, we build all proto's using LPI soldermask.

On the other hand, if your design is tolerant of thermal mask, AND your fabricator still uses it, then a color change makes no cost difference.  In this case, every unique design requires a screen setup/tear-down so the color of ink on the screen makes no difference.  However, if you ask for a color that is not used often, then you may have to pay for the special purchase whether you use it all or not.   Red, black and blue are common enough alternative choices.

As to whether a pcb shop charges for these costs or not varies.   

Hope this helps.   I think the different color on proto's vs production is a good idea and its often used.  Cost or not, its worth the lack of confusion of trying to read the fine print revision level in the copper circuitry.

Ron Huston
Advanced Circuits
Email: [log in to unmask]
www.4pcb.com

----------
From:  Doug McKean
Sent:  Thursday, March 02, 2000 4:33 PM
To:  [log in to unmask]
Subject:  [DC] Cost Differences of Different Colored Boards ...

Is there a cost difference for different
solder masks using say a red as opposed
to typical green color?

The suggestion is kicking around to signify
prototype boards with some color other than
green, and released production style boards
as ONLY green color.

Regards,  Doug McKean